A conventional numerical control apparatus has been known that provides for the verification of a machining program and the execution of machining of work at the same time by using the single block functionality, which sequentially executes or runs a machining program one block after another by depression of its start means. For example, the conventional numerical control apparatus shown in FIG. 7 includes a single block switch 52 and a start button 53 on an operation panel 51, in which a single block mode is set when the single block switch 52 is on and a continuous machining mode is on when the single block switch 52 is off. The numerical control apparatus additionally includes a machining program execution controller 54, a machining program interpreter 55, an interpolator 56, and machining program storage 57. Upon depression of the start button 53, the machining program execution controller 54 operates the machining program interpreter 55 and the interpolator 56.
Then, the machining program interpreter 55 sequentially reads the block data in a work program WP (see FIG. 6) stored in the machining program storage 57, interprets, and transmits the operation commands included in that data to the interpolator 56. The interpolator 56 determines the travel distance for each control unit time based on the current tool position, the machining endpoint position in the operation command, the tool feed speed, and other relevant information. The interpolator 56 then generates a positional command for moving the tool from the current tool position by the travel distance for each control unit time and sends the positional command to a servo-driver 59. The servo-driver 59 controls the servomotor 60, which serves as the driving mechanism of the machine tool, so as to move the tool to the position designated in the command. As the interpolator 56 repeatedly generates positional commands until the machining program reaches the end, the tool smoothly travels, thus machining the work to the desired shape.
In the single block mode, once one block is executed, the machining program execution controller 54 suspends its operation, not executing the next block until after the operator depresses the start button 53. In the mean time, the operator determines whether or not to execute the next block based on various information and conditions, including but not limited to information about the machining in the current and next blocks shown on the display and input unit 61, the current tool position, the remaining travel distance to the final machining endpoint, the rotational speed of the main spindle, the tool number, and the coolant supply condition. Since this single block functionality allows the operator to verify the suitability of the machining program on a block-by-block basis, it provides the advantages of smoothly machining first articles in particular in a trouble free manner. Conversely, in the continuous machining mode, a single depression of the start button 53 causes a plurality of blocks to be executed continuously.
Various techniques have been proposed to allow for more efficient verification of machining programs in numerical control apparatuses with this type of single block functionality. For example, Japanese Patent No. 2813079 discloses the technology for showing in animation the machining to be performed in the next block on a display and input unit. Japanese Published Unexamined Patent Application No. H06-75615 discloses the technology for automatically executing a plurality of blocks one after another at regular time intervals.